Steel cables and tie-rods are commonly anchored in the earth for use in strengthing various structures. These structures typically are retaining walls that are built to shore up embankments, highway lane divider walls, bridges and buildings for occupation. To anchor the end of one or more cables or tie-rods, a hole is first drilled into the earth. One end of the cables or the tie-rods is inserted into the hole which is then filled with grout which upon setting firmly anchors the embedded end of the cables or tie-rods in the earth.
The above description is a simplified explanation of the general procedure employed in anchoring cables and tie-rods. In actuality the grout or cement may not be simply poured into a hole about the cables and allowed to set since the grout will not compactly fill the various cracks, crevices and fissions that extend from the hole sufficiently to establish a sound structure. Also, merely pouring the grout would leave air pockets and holes in the anchor. Therefore, the grout has to be pumped under pressure in order to form a reliable, sound anchor that is firmly embedded.
Pumping grout under pressure into a hole in which cables and tie-rods are placed cannot be done by simply pumping a stream of the grout through a conduit into the hole. This is because the grout will simply flow out of the top of the hole once the hole has been filled without sufficient pressure existing in that portion of the grout that is within the hole. Because of this various apparatuses have heretofore been devised for use in this anchoring procedure.
As exemplified by the devices illustrated in U.S. Pat. Nos. 3,379,019, 3,735,541, 4,139,323 and 4,397,589, some anchor forming devices of the prior art have been designed so as to enable grout to be pumped under pressure, step by step, into a succession of hole spacial sections. Devices of this type have commonly employed an elongated tubular structure with a series of vertical outlets and valve means to enable grout to be pumped first into the bottom of the hole about the end of the tubular device while maintaining a seal about the tube and the walls of the hole. This approach is satisfactory in the sense that cables and tie-rods may be anchored with grout that is formed with sufficient pressure. However, a disadvantage of this aproach is that it takes a substantial amount of time and labor to form the anchor.
Another approach has been to utilize apparatus by which an upper portion of a hole is first grouted without significant pressure and allowed to set to form a seal. Grout is then pumped into the hole through the apparatus beneath the seal established by the upper layer of set grout to establish an embedded anchor in the bottom or end of the hole. Exemplary of apparatus used in this approach is that one shown in U.S. Pat. No. 4,386,876. This approach however is still beset with the same problem, namely the time involved in waiting for the unpressurized grout to set before the embedded anchor is formed.
It thus is seen that a need remains for an apparatus and for a method of anchoring cables, tie-rods and the like in the earth in a more expeditious and efficient manner. It is to the provision of such that the present invention is primarily directed.